Trouble Setting Default Version in Pythonista 3browsing

I have written a few simple scripts in Pythonista (original) which I use frequently on my IPhone 5s running iOS 9.3.2.. I have just upgraded to Pythonista 3 and want to set the default version to 2.7. The documentation says this can be done in the settings. I assume this refers to the Apple settings app, but Python 3 does not show up there. (Pythonista did.) I have also tried using the shebang method described in the documentation by adding "#1 python2" (but no quotes) as the first line to the scripts. When I try to running the scrips, I get formatting error messages. Do anyone have any suggestions of where I may have gone astray? (All is not lost -- the scripts do run using the tap and hold the run button and select 2.7 method.)